(a) Technical Field of the Invention
The present invention generally relates to circuit breaking devices, and more particularly to an improved circuit breaker structure that returns the circuit breaker back to the OFF state automatically.
(b) Description of the Prior Art
The ordinary circuit breakers utilize the ON and OFF action mechanism to prevent overheating, fire, and other hazardous accidents as a result of current overloading in electrical circuitries. The circuit breaker also has the characteristic of being able to return back to closed-circuit state after overloading condition is eliminated. However, safer, simplified operating mechanism and lower cost are still pursued by circuit breaker manufacturers.
Reviewing two previously awarded patent rights can provide an understanding of the mechanisms and shortcomings of prior arts of making circuit breakers.
The first one reviewed is Patent Number 208384, A Circuit Breaker Structure with Protective Circuit. Its main structure consists of three sets of plates. The center plate has a platinum point on it. The side plate also has a platinum point on it and a spring riveted to it. The center plate and the side plate make contact with each other at the two platinum points. The raised edge of the riveted spring then touches a curved spring. The slot at the lower portion of another moving plate is grooved between the raised edge of the riveted spring and the platinum point on that plate. The other end of this moving plate is inserted into a push-shaft through a hole to form a lever. The high temperature from current overloading makes the lever under the push-shaft to rise up and press the push-shaft, causing the separation of the two platinum points on the center plate and the plate with riveted spring, which in turn opens the circuit and stops the current flow. There is an adjustment screw inside the groove of the curved spring which can be used to make minute adjustment of the angle of the curved spring according to specified load values of voltage and amperage.
Next, following characteristics can be found in Patent Number 540812, Safe Circuit Breaker Lever Structure. This design features a chamber designed for the movement of an alloyed lever. The alloyed lever connects the switching element of the ON/OFF action with the open-close structure made of alloyed plates. The operating steps are depicted below:
First, under normal operating conditions, the ON/OFF action of the switching element is completed in a single movement and does not involve the alloyed lever.
Secondly, when current flows in the ON state, the alloyed lever expands freely in the chamber under heating which is generated from current flowing through the open-close structure of this circuit breaker. When the alloyed lever expands to a preset point, it will separate from the switching element, and the circuit breaker goes into the OFF state to avoid fire hazard from current overloading.
Thirdly, after the factors causing overloading are removed while the circuit breaker is at the OFF state, the switching element must be pressed once to make the alloyed lever to go into the opposite direction and return the circuit breaker to its normal OFF position.
As described in the aforementioned manner, the safe circuit breaker lever structure indeed do cut off the current flow under overloading condition to prevent overheating and assure safe electrical operation. Both steps 1 and 2 are normal and reasonable in the usual power switch devices. However, according to what is stated in step 3, in order to get the circuit breaker back to the normal OFF state requires a pressing action on the switching element, which is an unnecessary and spurious step. To start the circuit breaker to conduct current again, an operator needs to press the switching element again. Therefore, it takes two steps to re-start the electrical circuit. It is for this reason the construction of a chamber for moving lever needs further improvement and simplification.